Women, particularly menopausal and post-menopausal women, often experience a wide variety of conditions and disorders attributable to estrogen deprivation. Estrogen deprivation is often associated with the loss of ovarian function. This may result in hot flashes, dryness of the vagina, discomfort during intercourse, loss of bone mass, increased heart disease and the like.
Providing dosages of estrogen is an effective agent for the control or prevention of such conditions, particularly in controlling or preventing hot flashes and vaginal atrophy, along with retarding or preventing osteoporosis. Estrogen is typically administered alone or in combination with a progestin.
As detailed in U.S. Pat. No. Re. 36,247 to Plunkett et al., estrogen alone, given in small doses, on a continuous basis, is effective in most patients for the control of the above symptoms and problems associated therewith. However, although the vast majority of women taking continuous low-dose estrogen will not have bleeding for many months or even years, there is a distinct risk posed by this routine of developing “hyperplasia of the endometrium”. This phrase refers to an overstimulation of the lining of the uterus which can become pre-malignant, coupled with the possibility that the patient may eventually develop cancer of the uterine lining even under such a low-dose regimen (Gusberg et al., Obstetrics and Gynaecology, 17, 397–412, 1961).
Estrogen alone may be given in cycles, usually 21–25 days on treatment and 5–7 days off treatment. When small doses of estrogen are required to control the symptoms generally only about 10% of women experience withdrawal bleeding between the cycles of actual treatment. However, the risk of developing endometrial hyperplasia and the increased relative risk of developing cancer of the uterus may still be present with this method (Research on the Menopause: Report of a W.H.O. Scientific Group, 53–68, 1981).
The addition of a progestin for the last 7–10 days of each estrogen cycle helps to reduce concerns about developing endometrial hyperplasia and/or also reduces the risk of developing endometrial carcinoma below that of the untreated general population. However, withdrawal bleeding may occur regularly in this routine and this is generally not preferable to most older women (Whitehead, Am. J. Obs/Gyn., 142,6, 791–795, 1982).
Another routine for estrogen administration may involve a formulation such as those found in birth control pills which contain relatively small doses of estrogen over the full 20–21 day treatment cycle, plus very substantial doses of potent progestins over the same period of time. This routine, of course not only produces withdrawal bleeding on each cycle, but is also generally unacceptable because such formulations have been shown to carry an increased risk of developing arterial complications, such as stroke or myocardial infarction in older women about the age of 35–40. This is especially true if the individual is a smoker of cigarettes (Plunkett, Am. J. Obs/Gyn. 142,6, 747–751, 1982). Thus, there remains a need for novel isolated estrogenic compounds.